Epidemiological research shows wide agreement that comorbid disorders are the rule, rather than the exception. Substance abuse treatment programs typically report that 50 to 75 percent of their clients have comorbid psychiatric disorders. Treatment for comorbid disorders can be effective; however, the benefits are often not realized because persons typically fail to stay in treatment long enough to achieve any clinical benefits. The results of prior studies examining the relationship between psychiatric comorbidities and substance abuse treatment retention are inconclusive, due to methodological limitations, and have not been replicated. The aims of this study are: 1) to examine the relationship between psychiatric comorbidities and retention in substance abuse treatment; 2) to examine the relationship between service needs (medical, mental health, family, vocational, childcare, financial, social relations, and housing) and retention in substance abuse treatment among persons with and without psychiatric comorbidities; and 3) to test the contribution of service-need matching on retention in substance abuse treatment for persons with and without psychiatric comorbidities. This study uses data from the National Treatment Improvement Evaluation Study (NTIES), 1992-1997 - a prospective study of the impact of drug and alcohol treatment on vulnerable populations. The primary analytic strategy involves survival analysis with robust estimation methods. The proposed research will help identify factors that are associated with substance abuse treatment retention, including the role of psychiatric comorbidities, service needs, and service matching. This is important for developing interventions and policies that will increase the number of clients who complete an adequate amount of treatment. By building a greater understanding of the effectiveness of comprehensive service packages in substance abuse treatment, this research will help guide the use of limited treatment dollars. Taken together, this research contributes to the general knowledge about substance abuse treatment process, addressing the wide recognition that greater attention needs to be paid to questions of process rather than outcomes. This research will also equip a new investigator with the substantive, methodological and analytic skills to pursue a career in research focusing on quality of care and services for persons with comorbidities. [unreadable] [unreadable] [unreadable]